Crumar Bit 99 keyboard mcu failure

I have been working on bringing my Bit 99 back to life with some success. I . I had a problem with no midi or mod/bend wheel operation but, yesterday the keyboard stopped working and this led to me replacing the 8051 under the keybed. Immediately this resolved all the midi ,pitch bend and mod wheel problems. I think the 8051 must have been providing a clock to the midi interface chip on the main board. Now, however the keyboard no longer works, I presume this is because the new 8051 needs to be programmed appropriately. My question is, how on earth do I do that? I am reasonably experienced with electronics but I feel I have got to the end of, and probably dangerously beyond, the limits knowledge and would greatly value anyone’s greater expertise.
Thanks in advance!